It is known that the wheels of vehicles are generally made up of a cylindrical metal rim having, at the axial extremities, annular flanges between which is defined a channel for the slot-in fitting of an elastic tyre, the side portions of which, so-called “beads”, are stopped up fast on the annular flanges themselves.
Also known is the need to perform frequent balancing operations which consist in fitting specific balancing weights, made of lead or other material, in correspondence to predetermined points of the wheel and along the rim and the need to check the wheel's inclination to roll correctly following a geometric test of the rim and the tyre.
The fitting of the balancing weights does in fact offset, during wheel rotation, the presence of any tyre and/or rim irregularities which would lead to vibrations or stresses during vehicle movement.
To perform such operations, balancing machines are commonly used comprising a base frame supporting a horizontal shaft, so-called “balancing shaft”, which is axially rotatable due to the action of motor means and on which the wheel rim is keyed by means of suitable engagement and centring parts.
The amount of wheel unbalance is determined during the rotation by suitable electronic or electromechanical devices, such as force transducers applied along the balancing shaft.
To the measurement of the unbalance must be generally added other characteristic measurements, such as the measurement of the roundness of the wheel, of the eccentricity of the wheel, of the level of wear of the tread, of the shape, of the rim or other wheel irregularities, normally taken by means of suitable measurement sensors with or without contact (i.e. optical sensors or feelers).
Once the necessary measurements have been taken, the machine is able to calculate the size and the position of the balancing weights to be fitted on the wheel rim to offset the wheel irregularities.
The balancing weights are usually fitted manually by an operator at one or more precise points of the wheel rim indicated by the machine.
These balancing machines of known type; however, do have a number of drawbacks.
To measure the unbalance, traditional machines have force sensors, of the load cell type with piezo ceramic effect, which have to inconveniently be arranged in correspondence to a pair of restraints or elastic supports by means of which the shaft-bearing structure is fastened to the base frame.
Such classic configuration is not always practical and easy to achieve and, in some cases, reaches a considerably high level of complexity that makes both assembly and any maintenance jobs difficult.
The type of force sensors used on common balancing machines, furthermore, is such as to permit detecting the oscillations of the balancing shaft to determine the wheel unbalance, but does not allow obtaining other pertinent information such as, e.g., its weight.
For this purpose, traditional balancing machines make use of information contained in an internal database in which are filed the weights of the main wheels available on the market with, naturally, the consequent problems tied to the approximation of such information which do not always reflect the real conditions of the actual wheel to be balanced.
Alternatively, the wheel weight can be entered manually by the operator with the consequent loss of time relating to the carrying out of weighing and data entering operations.